TitleAbstractYear(sorted ascending)
carcinogenic activity of particulate nickel compounds is proportional to their cellular uptake.particles (less than or equal to 5 micrometers) of the potent carcinogen crystalline nickel subsulfide were actively phagocytized by cultures of syrian hamster embryo cells and chinese hamster ovary cells. cells did not take up significant quantities of similar-sized particles of the noncarcinogen amorphous nickel monosulfide. the carcinogenic activity of this and other metal compounds appears to be proportional to their cellular uptake.19807394519
studies on hexosaminidase forms in chinese hamster ovary cells.the hexosaminidase forms present in chinese hamster ovary cells grown in culture were partially purified and their kinetic and physical properties were characterized. the cells were found to contain three hexosaminidase forms, which could be resolved by ion-exchange chromatography. these three forms, designated hexosaminidases i, ii and iii, had properties similar to those of human hexosaminidases a, b and c, respectively. hexosaminidase iii, like human hexosaminidase c, appears to be regulated ...19807398610
large-scale isolation of uv-sensitive clones of cho cells.we have isolated 54 ultraviolet light (uv) sensitive clones of chinese hamster ovary (cho) cells, including two from a parent cell line which is hypersensitive to ethyl methanesulfonate (ems) and is also sensitive to x rays. a replica plating technique was used for the isolation of two of the clones, and a semiautomated technique was used for the isolation of the other 52 clones. we have observed uv sensitization of up to 5-fold in the mutants relative to the parent in terms of the slopes of the ...19807404271
genetic analysis of the human cell-surface antigens expressed by a human-chinese hamster somatic cell hybrid. 19807405744
g1 and s phase mammalian cells synthesize histones at equivalent determine the effect of cell cycle position on protein synthesis, synchronized cell populations were metabolically labeled and the synthesis of the basic proteins, including histones, was examined by two-dimensional gel electrophoresis. exponentially growing s49 mouse lymphoma or chinese hamster ovary (cho) cells were separated into g1 and s phase populations by centrifugal elutriation, selective mitotic detachment, fluorescence-activated cell sorting, or a combination of these, and pulse-lab ...19807407911
evaluation of methods for determining 6-hydroxydopamine cytotoxicity.the toxic effects of 6-hydroxydopamine on the human neuroblastoma cell line sk-n-sh-sy5y(sy5y) and the chinese hamster ovary (cho) cell line were measured with five viability assays. four of the assays (attachment efficiency, plating efficiency, amino acid incorporation into acid-precipitable proteins, and trypan blue dye exclusion) showed higher drug susceptibility in sy5y cells than cho cells. only growth inhibition (proliferation index) gave results indicating greater sensitivity in cho cells ...19807409829
sodium butyrate affects expression of fibronectin on cho cells: specific increase in antibody-complement-mediated cytotoxicity.cellular fibronectin is expressed only at very low levels on the surface of the spontaneously transformed chinese hamster ovary (cho) cell line, as detected by immunofluorescence studies and confirmed by resistance of cho cells to complement-mediated lysis in the presence of anti-fibronectin antibody. treatment of cho cells with sodium butyrate results in a marked susceptibility to anti-fibronectin complement-mediated killing. using selected complement-containing sera from rabbits, it is possibl ...19807410488
a novel synergistic effect of alanosine and guanine on adenine nucleotide synthesis in mammalian cells. alanosine as a useful probe for investigating purine nucleotide metabolism.a novel synergistic effect of the antitumor agent alanosine (2-amino-3-(hydroxynitrosoamino) propionic acid), which specifically inhibits the enzyme adenylosuccinate synthetase (ass) and guanine on the growth of chinese hamster ovary (cho) cells and human diploid fibroblasts (hdf) has been observed. in the presence of subinhibitory concentrations of alanosine, both cho cells and the hdf show excessive sensitivity to exogenous guanine--a phenotype which closely resembles that seen with some of th ...19807410492
human platelet lysate contains growth factor activities for established cell lines derived from various tissues of several species.factors have been studied from human platelets that promote the growth of a hormone-responsive rat mammary adenocarcinoma cell line mtw9/pl, the balb/c 3t3 mouse embryo fibroblasts, and numerous other established cell lines. a wide variety of the commonly employed cell lines, including lines of human, mouse, monkey, chicken, rat, chinese hamster, and syrian hamster origin, were tested for their growth response to a standard concentration of 200 microgram/ml human platelet lysate, and the lysate ...19807419237
facilitated transport of uracil and 5-fluorouracil, and permeation of orotic acid into cultured mammalian cells.the mode of permeation of uracil, 5-fluorouracil, and orotic acid into cells has been investigated in four established cell lines (novikoff rat hepatopma, p388 mouse leukemia, mouse l., and chinese hamster ovary cells) in attempts to assess the rate-determining step(s) in their incorporation into the nucleotide pool and nucleic acids. uracil and 5-fluorouracil shared a saturable transport system (km = 5 to 15 mm) capable of rapid equilibration of these substrates across the cell membrane (t 1/2 ...19807419607
patterns of chromosome segregation in chinese hamster x mouse cell hybrids between permanent cell lines and thymus cells.hybrids between a tumorigenic chinese hamster cell line (dc3f-aza) and normal mouse thymus cells very rapidly lost most of their mouse chromosomes, whereas hybrids between tumorigenic mouse cell lines (either cl.1d of l cell line origin, or pcc4-aza 1 teratocarcinoma cells) and normal chinese hamster thymus cells lost most of their hamster chromosomes. from three such fusion experiments, 20 cell lines were developed which all followed the same evolution, namely, the elimination of the majority o ...19807419611
heat-stable enterotoxin produced by yersinia enterocolitica isolated from patients.twenty-three strains of yersinia enterocolitica were isolated from children with gastrointestinal illness and examined for the production of enterotoxins by using both suckling mouse and chinese hamster ovary (cho) cell assay systems. six strains were found to be enterotoxigenic in the suckling mouse assay, but all strains were negative in the cho cell assay. enterotoxin was detected in the culture supernatant when organisms were grown at 25 c but not at 37 c. enterotoxin in a 15-fold concentrat ...19807432199
effects of long contact times of misonidazole on attached chinese hamster v79 cells.the 2-nitroimidazole misonidazole, an hypoxic cell radiation sensitizer, has been shown to be cytotoxic to attached oxic chinese hamster v79 cells after high doses and long contact times. this killing effect is enhanced if brdu is incorporated into chromosomes. it was found that misonidazole slows cell progression through the cell cycle and that those cells that move into mitosis carry very few chromosomal aberrations suggesting that the majority of cells are dying in interphase. the level of in ...19807432365
the use of organic solvents in mutagenicity testing.13 organic substances (dimethylsulfoxide, methanol, ethanol, n-propyl alcohol, sec-butyl alcohol, tert-butyl alcohol, dl-sec-amyl alcohol, ethylene glycol, ethylene glycol monomethyl ether, 1,4-diethylene dioxide, acetone, methyl acetate and formamide) were considered from the standpoint of their use as solvents for water-insoluble chemicals to be tested for mutagenicity. first, the effect of these solvents on cell survival was studied in the yeast schizosaccharomyces pombe and in v79 chinese ha ...19807432372
early capping of transcripts from the adenovirus major late transcription unit.the various events which result in modification of a primary rna transcipt may have a role in choosing transcripts which are to be processed into mrna. if there is a stepwise and interdependent nature to each of the modifications then it is important to place the various steps in temporal order. we show here that the formation of a capped 5' terminus seems to be a very early event for adenovirus type 2 (ad-2) nuclear rna that is initiated at the major late ad-2 promoter. there is an equally rapi ...19807432461
relationship between increased aerobic glycolysis and dna synthesis initiation studied using glycolytic mutant fibroblasts.reports from several laboratories have suggested increased rates of glycolysis play an essential part in the initiation of dna synthesis. this is based on observations that aerobic glycolysis: (1) occurs at low rate in resting mammalian cells and at very high rate in tumour cells; (2) increases rapidly after dna synthesis is initiated by addition of serum or purified growth factors, and (3) correlates with the expression of the transformed phenotype. also, specific inhibitors of aerobic glycolys ...19807432468
evidence for an adaptive dna repair pathway in cho and human skin fibroblast cell lines.when escherichia coli is chronically exposed to very low, nontoxic doses of a monofunctional alkylating agent (notably n-methyl-n'-nitro-nitrosoguanidine, mnng), the adaptive dna repair pathway is induced which enables the bacteria to resist the killing and mutagenic effects of further alkylation damage. mutation resistance in adapted bacteria is achieved, at least partly, by a greatly increased capacity of the cells to eliminate the minor dna alkylation product o6-methyl-guanine, which has been ...19807432501
a model system involving anti-concanavalin a for antibody targeting of diphtheria toxin fragment a1.results obtained in a model system strongly suggest that antibodies to cell surface determinants may be used to direct the toxic potential of the a chain of diphtheria toxin (dta). the a chain (m.w. 21,000) was covalently attached to antibody against concanavalin a (anti-con a) by means of a disulfide-containing cross-bridge. this dta-ss-(anti-con a) conjugate was toxic for 3t3 cells containing con a on their surface but was not toxic in the same concentration range for: (a) cells lacking con a; ...19807438043
the ultrastructure of centriole in mammalian tissue culture cells.structural polarity of centriole has been shown by analyzing serial sections of centrioles in the tissue culture cells of mouse, man, pig and chinese hamster. its major component is nine microtubule triplets. the inclination of the triplets towards the radius at the proximal end of the centriole is smaller than at the distal one. the internal tubule of the triplet has a smaller diameter than the middle and external ones; the triplets are bound by links of various nature all over their length. in ...19807438223
giant diploid oocytes as a cause of digynic triploidy in mammals.giant oocytes and zygotes twice the normal size from the chinese hamster were studied embryologically and cytogenetically in order to clarify their significance as a cause of digynic triploidy. there were 6 (0.62%) giant eggs among 973 primary oocytes, 5 (1.37%) among 365 secondary oocytes from mature follicles missing ovulation, 3 (0.44%) among 677 secondary oocytes from oviducts, 4 (0.45%) among 886 one-cell zygotes, and 3 (0.49%) among 608 two-cell zygotes. the results indicated that follicle ...19807438791
modulation of the nucleosome structure by histone acetylation.a rapid procedure for the isolation of core particles from chinese hamster ovary cells is described which permits measurements, usually at the day of their preparation. particles of 145 +/- 5 base pairs, derived from interphase cells, will be compared with the analogue specimens from butyrate-treated cells, metaphase cells and a standard preparation from chicken erythrocytes. butyrate cause an increase in the acetylation of histones h3 and h4, which induces alterations of the interhistone and hi ...19807439155
modulation by caffeine of enhanced postreplication repair in mammalian cells treated with shown previously, newly synthesized dna from chinese hamster, excision proficient and excision deficient xeroderma pigmentosum (xp) cells treated with split doses of n-acetoxy-acetylaminofluorene (aaaf) or ultraviolet radiation (uv) is larger in size than dna from cells treated with only the single dose. in this report we determined the effects of caffeine, an inhibitor of postreplication repair, upon enhancement of repair by a split dose treatment with aaaf. caffeine was added to cells eithe ...19807441110
comparative studies on chromosome aberrations induced by polycyclic hydrocarbons in cell-mediated and microsome-mediated assay.studies were made on chromosome changes in chinese hamster v79 cells induced by the polycyclic hydrocarbons, benzo[alpha]pyrene (bp), 3-methylchol-anthrene (mc) and 7,12-dimethylbenz[alpha]anthracene (dmba) in the presence and absence of cell-mediated and microsome-mediated activation systems. in cell-mediated assay, bp, mc and dmba induced concentration-dependent chromosome aberrations in v79 cells, at concentrations of 0.5--1.0 to 10.0 micrograms/ml in the presence of lethally irradiated syria ...19807442703
assignment of the gene for cytoplasmic glutamate-oxaloacetate transaminase to mouse chromosome 19 using chinese hamster x mouse somatic cell hybrids.chinese hamster and mouse cytoplasmic glutamate-oxaloacetate transaminase (got-1, ec were separated by isoelectric focusing of cell extracts on thin-layer polyacrylamide plates. the expression of mouse got-1 was correlated with the retention of mouse chromosomes and the expression of 16 marker isozymes in 77 chinese hamster x mouse somatic cell hybrids. mouse got-1 expression was discordant to the expression of isozyme genes assigned to mouse chromosomes 1, 2, 4, 5, 6, 7, 8, 9, 10, 11, ...19807444718
flow cytogenetic studies in chromosomes and whole cells for the detection of clastogenic effects.flow cytometric measurements of the chromosomal dna content have been used to develop a screening method for the detection of chemically- or physically-induced cytogenetic damage. the reproducibility of this flow cytogenetic assay was shown in a series of subcultures of a chinese hamster cell clone. the accuracy and sensitivity was tested in cultures treated with chemical mutagens and x-rays. the clastogenic effectiveness was quantified and the dose-effect relationship was established by the inc ...19807273960
the induction of mutation and differentiation in mammalian cells by chemicals which initiate or promote tumor formation.a cell-mediated mutagenesis assay was developed to predict the potential carcinogenic hazard of some environmental chemicals. in this assay, cells with appropriate markers for mutagenesis, such as the chinese hamster v79 cells, are co-cultivated with cells capable of metabolizing chemical carcinogens. use of this assay made it possible to demonstrate a relationship between the degree of carcinogenicity and mutagenicity of a series of polycyclic hydrocarbons, nitrosamines and aflatoxins, and to e ...19807030700
value of passive immune hemolysis for detection of heat-labile enterotoxin produced by enterotoxigenic escherichia coli.the method of passive immune hemolysis of evans and evans (infect. immun. 16:604-609, 1977) for detection of heat-labile enterotoxin produced by enterotoxigenic escherichia coli was modified. a total of 373 strains of e. coli were tested by this method using materials obtained by treating the cells with polymyxin b and rabbit antiserum against cholera enterotoxin, purified by affinity gel column coupled with purified cholera enterotoxin, in n-hydroxyethylpiperazine-n'-2-ethanesulfonic acid buffe ...19807031077
mutation and inactivation of cultured mammalian cells exposed to beams of accelerated heavy ions. iv. biophysical interpretation.a biophysical analysis is made of the results of recent experiments which used accelerated heavy ions of 20 to 470 kev micron-1 to induce inactivation and mutation (resistance to 6-thioguanine) in cultured v79 chinese hamster cells and hf19 human diploid fibroblasts. it is shown that the discrete nature of the primary ions must be explicity taken into account before the numbers of induced lethal and mutagenic lesions can be deduced from the observed radiosensitivities. the measured numbers of le ...19806966263
effects of temperature on sister chromatid exchanges.the influence of temperature on sister chromatid exchanges was investigated, and the results are discussed in connection with factors possible involved in temperature-induced sce-formation. whereas the sce frequency increased with increasing growth temperature in a cell line of xenopus laevis (eax), which permits the examination of great temperature differences, a chinese hamster cell line (v-79) revealed a u-shaped temperature-response curve. in addition, it was found that cold treatment at 4 d ...19807203467
effects of oxygen on pulmonary macrophages and alveolar epithelial type ii cells in culture.cultures of chinese hamster lung fibroblasts and explants of 20-day-old rat lungs were exposed to 95% oxygen with 5% co2 in vitro. the chinese hamster cells had stopped dividing after 17 hours exposure and cell death occurred at a mean time of 67 hours (s.d. 15 hours). the rat lung explants showed macrophages moving over a monolayer of alveolar type ii epithelial cells. both cell types appeared to function normally for 24 hours but cell division in the type ii cells was about 50% of control betw ...19807455401
enhancement of recovery of chemical carcinogen-induced ouabain-resistant mutants in chinese hamster cells by the tumor-promoting agent, 12-o-tetradecanoyl-phorbol-13-acetate.the effects of a tumor-promoting agent on the frequency of mutation to ouabain resistance and survival of chinese hamster cells treated with a chemical carcinogen have been investigated. 12-o-tetradecanoyl-phorbol-13-acetate (tpa) significantly enhanced the mutation frequency induced by the carcinogen, methylazoxymethanol acetate (mam), without having similar effects on cytotoxicity, at concentrations of 2 micrograms/ml or less. the observed degree of enhancement of mutagenesis increased with pr ...19807464841
[cytotoxicity of manganese for mammalian cells in vitro--comparisons with lead, mercury and cadmium].the effects of manganese chloride were studied in two human cell lines hela and human embryonic diploid fibroblasts in v79 chinese hamster lung cells, and l-a mouse fibroblasts. manganese produces a dose-dependent depression of proliferation along with a decrease of the mitotic rate. effects on viability are accompanied by increased release of the intracellular enzyme lactic dehydrogenase. lactic acid is stimulated indicating enhanced glycolytic activity. the colony forming ability and the rate ...19807467917
dna synthesis, mutagenesis, dna damage, and cytotoxicity in cultured mammalian cells treated with alkylating agents.the effects of n-methyl- and n-ethyl-n'-nitro-n-nitrosoguanidines and methyl and ethyl methanesulfonates on dna synthesis in c3h/10t 1/2 mouse embryo fibroblasts and chinese hamster v79 cells have been analyzed by measuring the incorporation of tritiated thymidine into the trichloroacetic acid-insoluble fraction and the purified dna of the cells, and by measuring the fraction of parental dna replicated by equilibrium density sedimentation in neutral cesium chloride gradients. the inhibition of d ...19807471086
size heterogeneity in the 3' end of dihydrofolate reductase messenger rnas in mouse cells.we have examined in detail the rna coding for dihydrofolate reductase (dhfr) in methotrexate-resistant mouse cells. we find four distinct dhfr messengers, ranging in size from 750 to 1600 nucleotides. all four are polyadenylated and polysomal and can be translated in vitro to produce a 21,000 dalton protein co-migrating with purified dihydrofolate reductase on sds polyacrylamide gels. the major difference in these rnas is the length of 3' untranslated regions, varying from about 80 nucleotides i ...19807448865
metabolism of benzo[a]pyrene in human epidermal keratinocytes in culture.the metabolism of benzo[a]pyrene (bp) in cultured human epidermal keratinocytes was investigated using thin layer chromatography, high pressure liquid chromatography and cell-mediated mutagenesis assay. epidermal keratinocytes were obtained from skin of normal subjects and all experiments were performed on primary cultures. human epidermal keratinocytes were shown to metabolize bp. analysis of bp metabolites by high pressure liquid chromatography indicated that epidermal keratinocytes metabolize ...198011219830
induction of sister chromatid exchanges by carcinogens mediated through cultured rat liver epithelial cells.a cloned, untransformed rat liver cell-line, lnrl (with the normal diploid karyotype and epithelial morphology) was tested for use as the metabolizing component in a co-cultivation system for carcinogen-screening using sister chromatid exchanges (sce) as the criterion. the well characterized early cultures of lnrl cells were co-cultivated with chinese hamster ovary (cho) cells, the target commonly used for the induction of sce, and exposed to different concentrations of various chemicals for 24 ...198011219869
characterization of a mutator gene in chinese hamster ovary cells.we have recently reported the isolation of a class of mutants (called thy-) that is both resistant to arabinosyl cytosine and auxotrophic for thymidine. thy- mutants have a 5- to 10-fold elevated pool of dctp and are deficient in the synthesis of dttp as an apparent consequence of a single mutation in the gene for ribonucleoside-diphosphate reductase (2'-deoxyribonucleoside-diphosphate:oxidized-thioredoxin 2'-oxidoreductase, ec here we show that three independent thy- lines have a 5- ...1980293738
high frequency of mutation to tubercidin resistance in cho cells.the acquisition of high-level resistance to tubercidin (an adenosine analog) in cho cells occurs in a single step at high frequency (10(-3) to 10(-4)) without mutagenesis. analysis of a large number of independent mutants by a fluctuation test (luria and delbruk, 1943) indicates that they arise independently of the selection medium and all fall into the same complementation group. all mutants tested lack detectable adenosine kinase activity. an analysis of hybrids between mutant and wild-type ce ...1980294700
disappearance of a structural chromatin protein a24 in mitosis: implications for molecular basis of chromatin condensation.a chromatin protein, a24, a conjugate of histone h2a and evolutionally conserved ubiquitin, was virtually the only structural polypeptide that was present in interphase but missing in mitosis of a chinese hamster cell line (don). because a 10% increase in the h2a/dna ratio observed in interphase-mitosis transition explained the stoichiometric conversion of a24 to h2a, it appears that ubiquitin bound to h2a of nucleosomal surfaces in interphase is released at mitosis whereas the total h2a remains ...1980293727
acetylation of spermidine in chinese hamster ovary cells. 19807213369
synthesis of the n-linked oligosaccharides of glycoproteins. assembly of the lipid-linked precursor oligosaccharide and its relation to protein synthesis in vivo.the asparagine-linked oligosaccharides of chick embryo fibroblast glycoproteins were previously shown to derive from a common lipid-linked precursor, glc3man9glcnac2. the formation of this precursor oligosaccharide was examined in intact chick embryo fibroblasts, nil-8 cells, and chinese hamster ovary cells. the labeling kinetics and compositions of the lipid-linked oligosaccharides were examined, and the results indicate that lipid-linked man5glcnac2 is rapidly assembled (< 1.5 min) and then ex ...19807440570
the use of a quantimet image analysis system to analyse trypsin banding patterns of v79/4 (ah1) chinese hamster chromosomes.a quantimet image-analysis system was programmed to identify and print out banding patterns from g-banded chromosome spreads of a clone derived from the established cell line v79/4 (chinese hamster fibroblasts), designated v79/4(ah1).19807202638
comparative studies of zinc metabolism in cultured chinese hamster cells with differing metallothionein-induction capacities.previous work in our laboratory led to the isolation of a cadmium (cd)-resistant variant (cd(r)2c10) of the line cho chinese hamster cell having a 10-fold greater resistance to the cytotoxic action of cd(2+) compared with the cho cell. this resistance was attributed to an increased capacity of the cd(2+)-resistant cd(r)2c10 subline to induce synthesis of the cd(2+)- and zn(2+)-binding protein(s), metallothionein(s) (mt). evidence that cd(2+) behaves as an analog of the essential trace metal, zn( ...198024271403
a genetic complementation study of purine analogue resistance in chinese hamster fibroblasts. 19807464849
relationship between chemical damage of dna and mutations in mammalian cells. i. dose-response curves for the induction of 6-thioguanine-resistant mutants by low doses of monofunctional alkylating agents, x-rays and uv radiation in v79 chinese hamster cells.the shape of the dose-response curve for mutations induced at low doses of mutagenic agents in mammalian cells was studied. with the exception of x-rays and mms, which are very toxic in relation to their mutagenic potency, dose-response studies with ems, mnu, enu and uv radiation were performed at doses giving about 100% survival. the results from several experiments were pooled for each agent to get higher resolution power at low doses, and the result was compared with what could be expected wh ...19807464843
in vivo interaction of anti-cancer drugs with misonidazole or metronidazole: cyclophosphamide and bcnu.the addition of misonidazole (miso) or metronidazole (metro) to treatment with cyclophosphamide (cy) increased delay to regrowth of 2 experimental tumours. the effect was observed for large an small tumours, was present for doses of miso that are ineffective for killing hypoxic cells, and required that it be given with, or shortly before cy. mice receiving combined treatment had more weight loss and myelosuppression than those receiving cy alone, and the therapeutic index was lower. miso caused ...19807459221
a proposed operational model of thermotolerance based on effects of nutrients and the initial treatment temperature.the phenomenon of thermotolerance in mammalian cells has been extensively documented in the literature. because of its potential clinical importance as well as the fundamental biological interest, we pursued additional studies investigating ph and nutritional effects. split-dose experiments were performed using plateau phase chinese hamster ha-1 cells. the effects of the nutritional environment during the initial 43 degrees incubation and the second 43 degree treatment on the induction of thermo ...19807438083
inhibition of mutagenesis in chinese hamster v-79 cells by antioxidants.the mutagenicity of benzo(a)pyrene (bp) on chinese hamster v-79 cells cocultivated with x-irradiated hamster embryo cells was inhibited by phenolic antioxidants, such as tert-butyl-4-hydroxyanisole (bha) and butyl-hydroxytoluene (bht), but not by disulfiram and its related compounds such as tetraethylthiuram disulfide, diethyldithiocarbamic acid and dimethyldithiocarbamic acid. the mutagenicity of bp on v-79 cells was reduced 44% by bha and 25% by bht. bha inhibited bp-induced mutagenesis, but n ...19807292522
selection of mitotic chinese hamster ovary cells from microcarriers. 19807224150
linkage in cultured chinese hamster cells of two genes, emtb and leus, involved in protein synthesis and isolation of cell lines with mutations in three linked genes.we have determined via segregation analyses from appropriate hybrids that two genes involved in protein synthesis, one encoding for a ribosomal protein (emtb) and one encoding for leucyl-trna synthetase (leus), cosegregate at a very high frequency and are linked in both chinese hamster ovary and lung cells. in contrast, the emta locus, defined by a second complementation group of emetine-resistant mutants which also have alterations affecting protein synthesis and probably the ribosome, is not l ...19807193212
structure-activity relationships in the development of hypoxic cell radiosensitizers. iii. effects of basic substituents in nitroimidazole sidechains.the effects of substituting 2-nitroimidazoles with groups carrying basic functions were studied. prototropic, redox, lipophilicity and protein-binding properties were compared with the efficiency in radiosensitizing hypoxic chinese hamster v79-379a cells in vitro and the cytotoxicities of the compounds after chronic aerobic exposure. seventeen compounds were (2-nitro-1-imidazolyl)alkylamines in which the effects of changes in the terminating base and of alkyl chain length were investigated. abou ...19806970731
relationship between membrane fluidity and capping of receptors for concanavalin a.the activities of a range of phenylalaninol-related compounds on capping of concanavalin a and induction of rounding of chinese hamster ovary tshl cells, as well as on the fluidity of phosphatidylcholine-cholesterol (1:1) liposomes, have been examined. these compounds include phenylalaninol, histidinol, leucinol, benzyl alcohol, benzylamine, 2-phenylethanol, 2-phenylamine, 3-phenyl-1-propanol, 3-phenyl-1-propylamine, and 3-phenylpropionic acid. the results indicate a strong correlation between t ...19806265046
esr studies on membrane fluidity of chinese hamster ovary cells grown on microcarriers and in suspension. 19806256190
copper chelator enhancement of bleomycin cytotoxicity.bleomycin's effects on dna strand scission are inhibited by low concentration of some metal ions (including copper), greatly stimulated by ferrous (fe+2) ions, and increased and probably mediated by the production of superoxide radicals (o2-), hydroxyl radicals (oh), and hydrogen peroxide (h2o2). however, the role of these mechanisms in overall bleomycin cytotoxicity is not known. for this reason, we have treated the chinese hamster cell line (v79) cells with a copper chelator, diethyldithiocarb ...19806159962
effect of heat shock on rna polymerase activities in chinese hamster ovary cells. 19806162461
permeation of chinese hamster ovary cells by glycerol: mechanism and kinetics.when monolayer cultures of chinese hamster ovary cells were exposed to 3h-glycerol ranging in concentration from 0.1 microm to 200 mm, glycerol in flux was found to increase in direct proportion to the extracellular concentration of glycerol. other experiments indicated that the same relationship existed at concentrations in excess of 1.0 m. similarly, glycerol efflux was found to vary in direct proportion to the intracellular concentration of glycerol. in neither case could influx or efflux be ...19807452723
mammalian cells do not have a stringent response.a key attribute of the stringent response of bacteria is the rapid inhibition of ribosomal rna synthesis mediated by unusual nucleotides in respnse to uncharged trna. the question as to whether mammalian cells show a stringent response analogous to that of bacteria was critically tested by the effective rapid amino acid starvation of both normal and transformed cells. rapid starvation giving a high proportion of uncharged trna for leucine was produced within 7 minutes of expression of a nonleaky ...19807462330
enzyme induction in a temperature-sensitive cell cycle mutant of chinese hamster fibroblasts.a temperature-sensitive (ts) cell cycle mutant of chinese hamster fibroblasts with a block in g1 was investigated. attention was on the expression of the activity of three enzymes: ornithine decarboxylase (odc) s-adenosylmethionine decarboxylase (samdc), and thymidine kinase (tk). odc and samdc activities are normally induced in the middle of, or late in, the g1 phase, while tk activity starts to appear at the g1/s boundary. in the ts mutant released from serum starvation at the nonpermissive te ...19807462327
heat and radiation sensitivity of chinese hamster v79 cells and of nine clones selected from survivors of a thermal tolerant cell population. 19807462062
effects of lucanthone on chinese hamster v-79 cells. ii. damage to dna. 19807462056
effects of lucanthone on chinese hamster v-79 cells. i. interaction with radiation in monolayers and spheroids. 19807462055
separation of large quantities of chinese hamster chromosomes by velocity sedimentation at unit gravity followed by blow sorting (facs ii). 19807449845
pyruvate blocks expression of sensitivity to antimycin a and chloramphenicol.selectivity in chinese hamster cells with antimycin a and chloramphenicol depends on a metabolic balance which can be modulated by varying the level of exogenous pyruvate. the effects of both inhibitors are most clearly seen in pyruvate-free nutrients. addition of 1 mm pyruvate in plating assays shifts dose-response curves for antimycin a or chloramphenicol to higher concentration levels and reduces the differential in response between sensitive and resistant cells. in mass populations, growth i ...19807444717
antipain and 12-o-tetradecanoyl-phorbol-13-acetate: phenomenology of effects on uv mutagenesis in v79 chinese hamster cells.antipain (ap) and 12-o-tetradecanoyl-phorbol-13-acetate (tpa) were tested in v79 chinese hamster cells for cytotoxicity and effects on survival and 6-thioguanine-resistant (6-tgr) mutation after uv-irradiation. ap and/or tpa were relatively non-cytotoxic and had no significant effects on uv survival. despite their non-mutagenicity, the recovery of uv-induced 6tgr colonies was significantly enhanced by the pretreatment with either ap (0.5-2 mm) or tpa (0.1-1 microgram/ml) only during the expressi ...19807254217
thymidine resistance in chinese hamster v79 cells in vitro.thymidine resistance in v79 chinese hamster cells has been investigated. phenotypically stable variant resistant lines occurred at a high frequency, and the mutation rate (2.67 x 10(-3) per cell per generation) to 400 micrograms/ml thymidine resistance as measured by the standard luria--delbrück fluctuation analysis was extremely high. populations of cells maintained for extended periods in f-10 medium spontaneously increased in resistance, possibly as a result of selective pressures due to the ...19807254216
busulphan-induced chromosomal aberrations in intestinal cells of chinese hamster.chinese hamsters were given busulphan, 25 and 50 mg/kg bw. after 18 h, chromosomes of the lining cells of the upper intestinal tract were prepared according to a newly developed method. the aberration rate was enhanced by a factor of about 25 after 25 mg/kg, but 50 mg/kg bw did not induce higher aberration rates. in the same animals the dose-dependent aberration rates were also determined in bone-marrow cells. furthermore, the formation of sces in intestinal cells was observed. in a preliminary ...19807219430
nitrosated urea pesticide metabolites and other nitrosamides. activity in clastogenicity and sce assays, and aberration kinetics in chinese hamster v79-e cells.the nitrosoureas 1-methyl-1-nitroso-3-phenylurea, 1-ethyl-1-nitroso-3-phenylurea, 1-methyl-1-nitroso-3-(p-fluorophenyl)urea, 1-methyl-1-nitroso-3-(p-chlorophenyl)urea, and 1-methyl-1-nitroso-3-(p-bromophenyl)urea, as well as their non-nitrosated parent compounds, were checked for induction of chromosomal aberrations and sister-chromatid exchanges in v79-e cells without metabolic activation in vitro. for comparison, methylnitrosourea, ethylnitrosourea and nitrosocarbaryl were included in this stu ...19807219429
influence of ph on the response of cells to single and split doses of hyperthermia.the time course of development and loss of thermotolerance in chinese hamster ovary cells exposed to 42 degrees was determined. the influence of ph on the heat sensitivity of normal and thermotolerant cells was examined. exposure of cells to single graded heat treatments at ph 7.4 resulted in a decrease in survival to 5 to 10% after 3 to 4 hr treatment. continued heating for an additional 4 to 5 hr resulted in an additional decrease in survival by a factor of only 1 to 2. at ph 6.7, exposure of ...19807193512
inhibition of x-ray-induced potentially lethal damage (pld) repair by cordycepin (3'-deoxyadenosine) and enhancement of its action by 2'-deoxycoformycin in chinese hamster hai cells in the stationary phase in vitro. 19806969408
enhanced killing of mammalian cells by radiation combined with m-amsa.m-amsa is an intercalating agent at present on phase ii trial as a chemotherapeutic drug. a 30 min exposure of chinese hamster (line v79-753b) cells to submicromolar concentrations of m-amsa killed 50% of the cells. the survivors had an enhanced sensitivity to radiation-induced cell killing. depending upon the conditions, m-amsa enhanced the radiation effect by either a decrease in the survival-curve shoulder or by an increase in slope. m-amsa may act partly by suppressing the accumulation of su ...19806893934
[causes of the preferential action of imuran on the viability and proliferative activity of a chinese hamster cell culture in the stationary growth phase].it has been shown that the active principle of imuran, 6-mercaptopurine, exerts a similar though less pronounced effect on viability and proliferative activity of chinese hamster cells by affecting them preferentially in the stationary phase of growth. this effect cannot be attributed to the inhibition by imuran of xanthine oxidase, as proposed earlier, since another inhibitor of this enzyme, allopurinol, appears more effective, causing more cell deaths during exponential growth phase rather tha ...19806893772
relative mutagenicity of antineoplastic drugs and other alkylating agents in v79 chinese hamster cells, independence of cytotoxic and mutagenic responses.the mutagenic and cytotoxic effects of 4 antineoplastic drugs, vinblastine, vincristine, adriamycin and nitrogen mustard and of several monofunctional alkylating agents have been assayed in v79 chinese hamster cells. vincristine, vinblastine and nitrogen mustard did not significantly increase the frequency of tgrhgprt- mutants but were were all highly cytotoxic. adriamycin and the monofunctional alkylating agents were all significantly mutagenic even at the lowest doses tested (approx. 70% survi ...19806265771
the pleiotropic effects of 33258-hoechst on the cell cycle in chinese hamster cells in vitro. 19806161017
a search for protein cores in chromosomes: is the scaffold an artifact?a protein chromosome scaffold structure has been proposed that acts as a structural framework for attachment of chromosomal dna. there are several troubling aspects of this concept: (1) such structures have not been seen in many previous thin-section and whole-mount electron microscopy studies of metaphase chromosomes, while they are readily seen in leptotene and zygotene chromosomes; (2) such a structure poses problems for sister chromatid exchanges; and (3) the published photographs show a mar ...19806160765
electron spin resonance studies of changes in membrane fluidity of chinese hamster ovary cells during the cell cycle.electron spin resonance (esr) spin-label methods were used with 5-doxyl-stearic acid as a probe to investigate membrane fluidity of chinese hamster ovary (cho) cells during the cell cycle. a 35 ghz esr technique was developed to study membrane fluidity of intact cells. this technique requires only about 1/6 the amount of cells compared to the conventional spin-label techniques. with this technique we observed a cyclic change of membrane fluidity during the cell cycle of cho cells: cells in mitos ...19806251882
the effect of the tumour promoter 12-o-tetradecanoyl-phorbol-13-acetate (tpa) on uv- and mnng-induced sister chromatid exchanges in mammalian cells.the induction of sister chromatid exchanges (sce) by the tumour promoter 12-o-tetradecanoyl-phorbol-13-acetate (tpa) has been studied in v79 chinese hamster cells comparing control untreated cells with either uv-irradiation or mnng-treated cells. in untreated cells tpa induced sce at a very low concentration. an increase of approximately 50% over the level of spontaneous sce formation was observed. in uv-irradiated cells, tpa, when present after the uv-irradiation, significantly enhanced uv-indu ...19807251226
effects of argon ions on synchronized chinese hamster cells. 19807454979
cytotoxicity of adriamycin on aerobic and hypoxic chinese hamster v79 cells in vitro.mammalian cells (v79-379a) in suspension culture rendered chronically hypoxic showed greater resistance to adriamycin than exponentially growing aerobic cells. resistance to adriamycin increased as a function of the time cells were held under hypoxic conditions, with maximal resistance after 6 h. chronically hypoxic cells retained their resistance when reoxygenated, and did not return to their original sensitivity until they had been in air for 24 h. uptake of adriamycin was similar for chronica ...19807437289
effects of 5-thio-d-glucose on cellular adenosine triphosphate levels and deoxyribonucleic acid rejoining hy hypoxic and aerobic chinese hamster cells.intracellular adenosine triphosphate (atp) levels were measured in both hypoxic and aerobic cultures of v79 chinese hamster cells treated with 5-thio-d-glucose (5-sh-d-glc). this glucose analog, a known inhibitor of d-glucose transport and metabolism, reduced atp in cell cultures allowed to become hypoxic by cell metabolism, but not in aerobic cultures treated similarly. cells depleted of atp were unable to rejoin x-ray-induced deoxyribonucleic acid (dna) strand breaks as measured by the alkalin ...19807422846
excess thymidine is not mutagenic in chinese hamster v79 fibroblasts.the ability of thymidine to enhance the frequency of hgprt-, 6-thioguanine resistant v79 cell mutants has been investigated as a function of post treatment growth interval. we have also studied the relative sensitivities towards exogenous thymidine of wild type and mutant cell lines. our data imply that increases in mutant frequency following exposure of v79 cells to thymidine can be explained on the basis of a greater sensitivity of wild type cells compared with hgprt deficient cells.19807418011
inhibition of metabolic cooperation in chinese hamster cells by various chemical including tumor promoters.the effects of 12-o-tetradecanoyl phorbol-13-acetate (tpa) and other chemicals on the contact-feeding phenomenon were investigated. the death of 6-tgr cells was prevented by tpa even upon culture with 3 times as many wild-type cells as in tpa-free medium. seven out of 18 chemicals tested were shown to inhibit the phenomenon of metabolic cooperation. they were concanavalin a, lithocholic acid, chaetoglobosin a, 3-hydroxyanthranilic acid, urea, anthralin and saccharin. among known tumor promoters, ...19807227712
an investigation of the genetic toxicology of irradiated foodstuffs using short-term test systems--ii. sister chromatid exchange and mutation assays in cultured chinese hamster ovary cells. 19807203292
isolation and partial characterization of a cage of filaments that surrounds the mammalian mitotic spindle.mitotic cells have been detergent extracted under conditions that support microtubule assembly. when hela cells are lysed in the presence of brain tubulin, mitotic-arrested cells nucleate large asters and true metaphase cells yield spindles that remain enclosed within a roughly spherical cage of filamentous material. detergent-extracted mitotic chinese hamster ovary (cho) cells show a similar, insoluble cage but the mitotic apparatus is only occasionally stabilized. in later stages of mitosis, h ...19807191425
synergistic effects of epidermal growth factor and thrombin on the growth stimulation of diploid chinese hamster fibroblasts.the serum supplement used in the culture of a variety of mammalian cells can be replaced by known growth factors. diploid chinese hamster fibroblasts (chef/18) will grow for several days in a medium (4f) supplemented with four growth factors: epidermal growth factor (egf), insulin, fibroblast growth factor (fgf), and transferrin. the growth rate is only about 50% as fast as when fetal calf serum is added. this difference is eliminated by thrombin (10--100 ng/ml; 0.3--3 nm). the chef/18 cell line ...19807000801
negative pion irradiation of mammalian cells. iii. a comparative analysis of dna strand breakage, repair and cell survival after exposure to pi-mesons and x-rays.the yields of immediate and residual breaks in dna of x- and peak pion irradiated chinese hamster cells were measured by hydroxylapatite chromatography in order to investigate the r.b.e. of immediate break production and the relation between residual breaks and survival in the same low dose range of up to 10 gy. a linear dose response for immediate break induction was observed with an r.b.e. of 0.37 for peak pions, whereas the formation of residual breaks showed a linear-quadratic dose dependenc ...19806969231
postreplication repair and the susceptibility of chinese hamster cells to cytotoxic and mutagenic effects of alkylating agents.a cell variant (vr-43) resistant to the cytotoxic effect of n-methyl-n'-nitro-n-nitrosoguanidine and n-methyl-n'-nitro-n-nitrosourea was isolated from chinese hamster v79 cells for use in studies of the relationship among cell survival, mutagenesis, and dna repair by alkylating agents. resistance to ouabain or 6-thioguanine was used as the genetic marker. after treatment with n-methyl-n'-nitro-n-nitrosoguanidine, the vr-43 cells exhibited mutation frequencies that were lower, on a dose basis, th ...19806934532
modification of cell membrane in variants of chinese hamster cells resistant to abrin. 19806775967
morphological reverse transformation of chinese hamster ovary (cho) cells and surface fibronectin.alterations in the distribution of surface fibronectin during reverse transformation of chinese hamster ovary (cho) cells induced by dibutyryl adenosine cyclic monophosphate (dbcamp) and theophylline was examined by indirect immunofluorescence. dbcamp-induced reverse transformation was not followed by any significant increase in surface fibronectin up to 48 hrs after treatment. reverse transformation induced by theophylliner by itself or in combination with dbcamp is followed several hours later ...19806251978
response of chinese hamster ovary cells to dna damage after a conditioning exposure to ultraviolet light.[3h]thymidine pulse-labeling and pulse-chasing of dna in ultraviolet-irradiatied cells was examined in detail by alkaline sucrose gradient velocity sedimentation. in cells exposed to 2.5 j/m2 2 h earlier, a higher percentage of 3h-labeled dna accumulated at high molecular weight during the 1.5 h after 5.0 j/m2 than in cells exposed to 5.0 j/m2 alone. this increased percentage can be accounted for by the fact that there was already a component of 3h-labeled dna at high molecular weight at the tim ...19807407188
induction of surface glycoprotein expression by cyclic amp in chinese hamster ovary cells.surface expression of a membrane glycoprotein of 135,000 molecular weight (p135) was inducible by adenosine 3',5' -cyclic monophosphate in chinese hamster ovary cells, cho-k1 clone. cells were cultured in the presence or absence of cyclic amp derivatives, chemicals influencing cytoplasmic cyclic amp levels, or inhibitors of protein or rna synthesis. surface proteins wre radiolabeled by a lactoperoxidase-catalyzed iodination reaction and analyzed by two-dimensional polyacrylamide gel electrophore ...19806251908
mechanism of cyclic amp effect on nutrient transport in chinese hamster ovary cells. a genetic approach.the effect of 8-bromo cyclic adenosine 3':5'-monophosphate (8-br-camp) on sugar and amino acid transport was investigated in wild-type chinese hamster ovary (cho) cells and in mutants selected for resistance to camp inhibition of cell growth. in wild type cells, both 3-o-methyl-d-glucose and alpha-aminoisobutyric acid transport were decreased in cells treated for 24 h with 8-br-camp; kinetic analysis indicated that a decrease in vmax, without a significant change in km, accounted for the lower t ...19806251043
methotrexate-resistant chinese hamster ovary cells contain a dihydrofolate reductase with an altered affinity for methotrexate.previous reports [flintoff, w. f., davidson, s. v., & siminovitch, l. (1976) somatic cell genet. 2, 245--261; gupta, r. s., flintoff, w. f., & siminovitch, l. (1977) can. j. biochem. 55, 445--452] described a series of chinese hamster ovary cells that were resistant to the cytotoxic action of methotrexate and contained a dihydrofolate reductase that was less sensitive to inhibition by the drug than wild-type enzyme. in this study, binding of labeled methotrexate to the reductase--nadph complex a ...19807417407
sister chromatid exchanges and chromosome aberrations in v79 cells induced by aflatoxin b1, b2, g1 and g2 with or without metabolic activation.cells from chinese hamster cell line v79 were pulse treated for one hour with aflatoxin (af) b1, b2, g1 and g2 at various doses with or without the metabolic activation system-s9 mix. with metabolic activation, all these toxins caused significant increases of frequencies of sister chromatid exchanges (sce) in a dose-dependent manner. based on the rate of sce induction, the relative order of potency was established as afb1 > g1 > g2 > b2. without metabolic activation, all four toxins had no or ve ...198011219866
asbestos-induced sister chromatid exchanges in cultured chinese hamster ovarian fibroblast cells.asbestos fibers were tested for possible mutagenic activity using the fluorescent plus giemsa (fpg) sister chromatid exchange (sce) technique. amosite, crocidolite, and chrysotile fibers were added to cell cultures at final concentrations of 10 and 100 micrograms/ml. chrysotile completely inhibited cell growth at both concentrations; cells exposed to amosite and crocidolite proliferated but only at the lower concentration. crocidolite significantly elevated the sce rate and larger (greater than ...19807462909
genetic analysis of tumorigenesis: vi. chromosome rearrangements in tumors derived from diploid premalignant chinese hamster cells in nude mice.the chromosome constitution of chef/16 clones recovered from methylcellulose and of uncloned, tumor-derived chef/16 populations are compared. nine of 11 clones recovered from methycellulose were initiated by diploid cells. moreover, chromosomally diploid cells were still present in most chef/16 clones even after growth in anchorage-independent conditions. in contrast, none of the chef/16 cells recovered from tumors were diploid. nonrandom chromosome changes were observed, but no specific chromos ...19807434146
photoinactivation of chinese hamster cells by hematoporphyrin derivative and red light. 19807433532
protein synthesis and the presence of absence of a measurable g1 in cultured chinese hamster cells.v79-8 cells lack a measurable g1 interval under normal growth conditions. we found that partial inhibition of protein synthesis using low levels of cycloheximide (0.05 mu/ml) could induce a measurable g1 in these cells without any significant effects on s, g2, or m. in view of these findings, recessive mutants selected from the v79-8 cell line, which each express g1, were analyzed for their rates of protein synthesis and degradation/loss. three of the four mutants showed a decreased rate of prot ...19807419616
initial changes in cell cycle progression of chinese hamster v-79 cells induced by high-let charged particles. 19807413930
cho cells selected for phytohemagglutinin and con a resistance are defective in both early and late stages of protein glycosylation.the lipid-linked and asparagine-linked oligosaccharides of two lectin-resistant and one parental chinese hamster ovary (cho) cell line have been compared by glycosidase digestion and gel filtration analysis of radiolabeled glycopeptides and oligosaccharides. the additional glycosylation defect in a double mutant cell line (cho-pharconar) selected from a phytohemagglutinin-resistant single mutant cell line (cho-phar) for resistance to concanavalin a has been identified as a block in the synthesis ...19807407919
tests for dna and chromosomal damage induced by nuclear magnetic resonance imaging.chinese hamster ovary (cho) cells in culture were exposed in a nuclear magnetic resonance (nmr) imaging apparatus to a strong magnetic field, pulsed field gradients, and radio frequency emissions. no chromosomal aberrations were induced even after an exposure of approximately 14 hours. no sister chromatid exchanges were induced by four-hour exposures to either low (average 7.2 mw) or high (average 61.2 mw) radio frequency power. when hela cells were exposed for 16 hours to an average radio frequ ...19807403551
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